PMODIA_RM Datasheet, PDF (3/3 Pages) List of Unclassifed Manufacturers – Digilent PmodIA™ Impedance Analyzer Reference Manual

PmodIA Reference Manual
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Once you have set these parameters, perform
the following steps to start the frequency
sweep (paraphrased from the AD5933 data
sheet):
1) Enter standby mode by sending the
standby command to the control
register.
2) Enter the initialize mode by sending an
initialize with start frequency command
to the control register. This allows the
circuit being measured to reach its
steady state.
3) Start the frequency sweep by sending
the start frequency sweep command to
the control register.
Impedance Calculations
The analog-to-digital converter samples the
frequency response from unknown
impedances at up to 1MSPS with 12-bit
resolution for every point in the frequency
sweep. Before storing the measurements, the
PmodIA performs a Discrete Fourier Transform
(DFT) on the sampled data (1,024 samples for
each frequency step). Two registers store the
DFT result: the Real Register, and the
Imaginary Register.
Where |Z| is the magnitude and ∠θ is the
phase angle:
|ܼ| = ඥܴ݈݁ܽ^ଶ + ݕݎܽ݊݅݃ܽ݉ܫ^ଶ
∠ߠ
=
݊ܽݐ^ିଵ
ݕݎܽ݊݅݃ܽ݉ܫ
ܴ݈݁ܽ
The PmodIA does not perform any
calculations. After each DFT, the master
device must read the values in the Real and
Imaginary registers.
In order to calculate the true impedance you
must take into account the gain. You can find
an example gain factor calculation in the
AD9533 data sheet.
Temperature Readings
The PmodIA has a self-contained, 13-bit
temperature sensor to monitor device
temperature. Please refer to the AD5933 data
sheet for more information on controlling this
module.
Register Addresses
The AD5933 data sheet has a complete table
of register addresses.
Electrical impedance contains both real and
imaginary numbers. In Cartesian form, you can
express impedance with the equation:
ܼ = ܴ݈݁ܽ + ݆ ∗ ݕݎܽ݊݅݃ܽ݉ܫ
Where Real is the real component, Imaginary is
the imaginary component, and ݆ is an
imaginary number (equivalent to ݅ = √−1, in
mathematics). You can also represent
impedance in polar form:
ߠ∠|ܼ| = ݁ܿ݊ܽ݀݁݌݉ܫ
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